Low-pitched voices in electronic organs



N V- 4, 1969 I T. w. CUNNINGHAM 3,476,866

LOW-PITCHED VOICES IN ELECTRONIC ORGANS Filed Aug. 11, 1965 4 6 IMI 62 .33 Ilg 1.0022

84 7 INVENTOR THOMAS W. CUNNINGHAM ATTORNEYS United States Patent 3,476,866 LOW-PITCHED VOICES IN ELECTRONIC ORGANS Thomas W. Cunningham, Union Township, Clermont County, Ohio, assignor to D. H. Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Filed Aug. 11, 1965, Ser. No. 478,817 Int. Cl. G10h 1/02, 5/06 US. Cl. 841.26 20 Claims ABSTRACT OF THE DISCLOSURE This invention relates to electronic musical instruments and, in particular, concerns the simulation in a theatertype electronic organ of low-pitched sounds such as the sound of thunder, of a bass drum and the like.

Thunder sounds in theater pipe-organs have been simulated by using a pedal piston, which, when actuated caused a number of the lowest-pitched 'diaphone or tuba pipes of the pipe-organ to be sounded together, causing a loud rumble. This was a rather crude elfect, since the pipes stopped sounding abruptly when the piston was released.

According to the present invention, electronically simulated thunder has a somewhat similar steady-state effect to that produced by pipe organs in that it provides a low rumbling sound so long as the actuating switch is closed. However, a great improvement is accomplished in that, when the switch is released, the rumble continues in a slow decay down to no sound, with the higher frequency components decaying more rapidly. This produces the effect of thunder rolling off into the distant hills.

Although a blow on a bass drum produces a complex sound having a plurality of low-frequency components, it is characterized by a strike which immediately decays. However, as will be described in detail hereinafter, generically similar circuitry may be employed to achieve soundssuch as of thunder and of the bass drum.

Briefly, according to this invention, a plurality of unharmonic, low-pitched tone signals are gated individually through a plurality of direct-current-actuable, gradualdecay, diode gates having different decay rates and being activated by a common switch from a source of direct current. Thus a complex low-frequency beat pattern is obtained. After passage through a low-pass filter, the output of the gates is amplified and then converted to sound in conventional electroacoustic apparatus such as one or more loudspeakers. In the case of thunder sounds, the input to the preamplifiers, amplifiers and speakers may be such as to. cause distortion, creating also sum and difference frequencies of the original frequencies, thus adding to the complex low-frequency beats.

It is a primary object of the present invention to pro vide means for simulating thunder in electronic musical instruments.

It is a further object of the present invention to simulate thunder by means of relatively simple, inexpensive standard electronic components.

It is an important object to simulate not only the more-or-less steady-state or initial thunder sounds, but also to imitate the gradual roll-ofi such as occurs when 3,476,866 Patented Nov. 4, 1969 ice the initial sounds of thunder echo and reverberate from distant objects and terrain.

Another object of the invention is to provide a relatively simple and low-cost circuit for simulating in an electronic musical instrument the sound of a bass drum.

These and other objects which will be set forth hereinafter, or will be apparent to one skilled in the art upon reading this specification, will be described in an exemplary embodiment, reference being made to the accompanying drawing, wherein:

FIGURE 1 is a schematic diagram of an electric circuit for simulating thunder.

FIGURE 2 is a schematic diagram of an electrical circuit for simulating the sound of a bass drum.

Referring to FIGURE 1, four tone-signal sources, labeled C E G15 and B (32.7 to 61.7 c.p.s.), are preferably divider stages in a gamut of twelve conventional, cascaded flip-flops driven at their prescribed frequencies by a series of twelve, stable, master oscillators in an electronic organ. One side of each source is grounded to a common return path, as at 2. The output of each source may be connected to a pair of bacloto-back solid state diodes 4, 6, in series. A common collector 8 combines the gated signals for transmission to an output system comprising a low-pass filter, indicated generally at 10. The individual components in the filter 10 are resistors and capacitors, preferably of values as indicated in FIGURE 1. Capacitances are in microfarads and resistances are in ohms. The output of filter 10 is connected preferably to a preamplifier 12, a power amplifier 14 and loudspeaker(s) 16, all in series as shown.

Each pair of diodes 4, 6 is part of a group of signal gates 18, 20, 22 and 24, comprised each of the .0022 bypass capacitor connected between a ground point 26 and the junction between the diodes 4, 6 plus other components as follows. A l megohm resistor also connects the diode junction point to a common bus 28 to which is connected a common actuating switch 30, in series with a direct current source 32 which is grounded at 34. In series, however, with three of the 1 megohm resistors may be an additional isolating solid state diode 36, as shown. On the switch side of each 1 megohm resistor is a storage or decay capacitor-values being .47, .82, 1.0 and 2.0 as shown-connected to a ground point.

In operation, direct current from the source 32 is carried, upon closure of switch 30, via ground connections 34, 38 to the respective storage capacitors, the return to the source 32 being via isolating diodes 36 and bus 2 8. (The purpose of the isolating diodes is to keep the longer decay capacitors, which take longer to discharge upon release of switch 30, from discharging into the smaller ones via the bus 28.) As the charge builds up on the decay capacitors, the direct voltage is carried via the 1 megohm resistors to the diodes 4, 6 which are rendered conductive thereby to signals from the sources C E G# and B The gated signals are collected in bus 8 and passed through the filter 10, amplified by the preamplifier 12 and amplifier 14 for conversion to sound in the electroacoustic system 16. As mentioned above, the signals preferably cause distortion in the amplifiers and speaker to develop sum and differences frequencies. Upon opening of the switch 30, the charges on the respective decay capacitors decay at rates determined by the time constant of each gate. The larger capacitors allow the lower frequency signals to decay at slower rates than the higher frequency signals. This fact results in a more authentic simulation of natural thunder.

If the signals from sources C B Git; and B are low in complexityfor example sinusoidal-the lowpass filter 10 may be of less complexity, or may be dispensed with entirely, the filter 10 having as its primary function to eliminate harmonics of the generated tones. Also, it 'is not intended that the specific nomenclature signals disclosed be a limination. For instance, Cifi, F A and C could be used. Also, the use of four signals is not critical. For example, if a. less complex efifect is desired, three signals could sufiice. On the other hand, a more complex result could be obtained by using more than four signals. It is essential, however, that the time constants of the higher-frequency gates be shorter than those for the lower-frequency gates, so that, the higherpitched components decay more rapidly than the lower ones.

Referring now to FIGURE 2 for the preferred embodiment for bass-drum sounds, it can be noted that the gates 40, 42 and 44 are similar to gates 18 to 24 of FIG- URE 1 except for the decay capacitors, which in the former gates are .039, 0.82 and .33 microfarads, respectively. The gates are connected, as shown, to tone-signal sources labeled D Fit and E which correspond approximately in frequency ratios to the rates of vibration of stretched membranes given by Olson in Musical Engineering (McGraw-Hill, 1952, p. 78) as:

f =1.00; ;,,=2.30 and f03=3.60

Aside from the wider difference in pitch of the component tone signals, the principal difference between the circiuts of FIG. 2 and FIG. 1 is that the former has a pulse forming network 46 at the direct current input to the gates 40, 42, 44. A +100 volts is continuously applied via terminal 48 to one side of a .47 microfarad capacitor 50, the other side of which is connected via the pulse-input bus 52 to the gates 40, 43, 44, to which also are connected, as shown, a diode 54 and a K resistor 56. It will be noted that the diodes 58, 60 and 62 are also located in the pulse inputs of the gates 40, 42, 44. A single-pole, single-throw switch 64 is shown connected between the capacitor 50 .and a source (not shown) of direct voltage of -l00 volts at terminal 66.

As in the example of FIG. 1, the outputs of the gates 40, 42, 44 of FIG. 2 are carried by way of bus 68 to a low-pass filter 70, preamplifier 72, power amplifier 74 and loudspeaker(s) 76, all connected in series.

The operation of the circuit of FIG. 2 will best be preceded by describing the condition of the pulse-forming network 46 prior to closure of switch 64. At this time, the capacitor 50 is charged to 100 volts by the directcurrent source connected to terminal 48. Upon closure of the switch 64, the capacitor 50 is reverse-charged by the direct-current source'connectedto terminal 66. The instantaneous current flow is through capacitor 50 in series with theparallel combination of capacitors 79,, 80, and 81, and through the common returns 78, 82, 83, 84. The sum of capaictors 78, 81, 82 is essentially equal-to capacitor 50, leavingan equal change in voltage oneach opens the gates 40,42, 44 by rendering their respective back-to-back diodes conductive to signals from the sources D Fit and E respectively, which, in turn, decay at different rates as determined by the respective time constants of the gates.

The pulse-shaped envelope of the three signals is applied to thelow-pass filter viathe bus 68, and higher-frequency components are filtered out on a preferential basis as determined by the characteristics of the filter. This is believed to simulate the rapid decay of the higher modes of vibration of a drum-head, which are absorbed as drum head losses and are rejected by the cavity resonance of the drum interior.

The diodes 58, 60, 62 prevent (1) all the decay capacitors from discharging back into the pulse-forming network 46 and (2) the larger decay capacitors from discharging into the smaller ones.

As in the case of the embodiment of FIG. I, it is not intended that the specific circuitry and signal frequencies disclosed be limiting. For example, othernearby signals, such as those corresponding to F G and D3 could be used as well for achieving certain objects of this invention.

When the switch 30 is closed four frequencies are passed to the preamplifier 12. These four frequencies are unharmonically related. While the switch 30 remains closed, the four frequencies are heard. However, the difference between each pair of frequencies is heard as a beat, the highest beat being 61.732.7=29 c.p.s., and hence falling in the infrasonic range. The beats produce the rumble ofthunder, and are-themselves all unharmonic. The resultant signal is to the listener, quite complex. To increasethe complexity, the preamplifier 12 may be overdriven, which generates difference and sum signals, and harmonics. The filter 10 is then tailored to remove all frequencies above a predetermined value with a considerable roll off. Therefore, the second harmonic of C is passed, and some of the sum frequencies, and all the difference frequencies. The precise design of filter 10 is a matter of aesthetic choice, within the limits above prescribed, and the added frequencies generated give rise to additional beats, and hence again render the sound ultimately heard more complex.

When switch 30 is opened, the basic frequencies of the system decay at different rates, the higher frequencies more rapidly. As each frequency decays to subaudible level, the beats, harmonics and heterodyne products associated therewith also disappear, until eventually only C is heard and then this too disappears.

One skilled in the art will readily detect generic similarities between the embodiments of FIGURES l and 2. Both comprise a plurality of direct-current-actuable signal gates of varying decay rates fed by unharmonic, relatively low-pitched signals, the outputs of which gates are passed through a low-pass filter for amplification and conversion to sound.

Modifications may be made in the invention without departing from the spirit of it. For example, the diode gates could be of the type illustrated in the Brombaugh US. Patent 3,179,855. A disadvantage here would be that rather large coupling capacitors would be required. The scope of the invention is defined in the appended claims.

What is claimed is:

1. In an electronic musical instrument, the combination comprising:

a plurality of unharmonically related tone-signal sources,

7 an equal plurality of direct-current actuable, gradualdecay, tone-signal gates respectively coupled with said tone-signal sources,

a source of direct voltage,

a common switch connected between said sources of direct voltage and said tone-signal gates in parallel, and

an output system coupled to said tone-signal gates,

said tone-signal gates having audibly different decay rates as between one and another, the decay rates for respectively lower ones of all said frequencies being lower than the decay rates for respectively higher ones .of said frequencies and proportioned to produce a sound corresponding with the sound of bass drum and thunder.

2. The combination according to claim 1, including:

a pulse-forming network connected between said common switch and said tone-signal gates in parallel.

3. The combination according to claim 1, wherein said tone-signal gates comprise each.

a pair of back-to-back diodes coupled in series between one of said tone-signal sources and said output system, and

a relatively-high resistance and a decay capacitor coupled between a common return path and the junction between said back-to-back diodes, said direct voltage being applied via said common switch across said decay capacitors.

of said tone-signal gates, said further diodes being so poled as to prevent discharge of any one of'said decay capacitors toward a smaller capacitor.

5. The combination according to claim 4, wherein said further diodes are coupled in all except the highest frequency one of said tone-signal gates.

6. The combination according to claim 4, including:

a pulse-forming network between said common switch and said tone signal gates in parallel.

7. In an electronic musical instrument, the combination comprising:

a plurality of relatively-low pitched, non-harmonic tonesignal sources,

an equal plurality of direct-current-actuable, gradualdecay, tone-signal gates respectively coupled in series with said tone-signal sources,

a source of direct voltage,

a common switch connected between said source of direct voltage and said tone-signal gates in parallel, and

6 11. In an electronic musical instrument, the combination comprising:

a plurality of relatively-low pitched, non-harmonic tone signal sources, an equal plurality of direct-current-actuable, gradual- 4. In an electronic musical instrument, the combina- 5 i decay, tone-signal gates respectively coupled in series tion comprising: with said tone-signal sources,

a plurality of tone-signal sources, a source of direct voltage,

an equal plurality of direct-current actuable, graduala common switch connected between said source of decay, tone-signal gates respectively coupled with 10 direct voltage and said tone-signal gates in parallel, said tone-signal sources, and

a source of direct voltage, an output system coupled to said tone-signal gates,

a common switch connected between said source of whereby to obtain in said output system a complex direct voltage and said tone-signal gates in parallel, low-frequency beat pattern with a gradual decay and upon opening of said common switch, wherein said an output system coupled to said tone-signal gates, tone-signal gates comprise each:

said tone-signal gates having different decay rates a pair of back-to-back diodes in series between one of as between one and another, wherein said tone-signal said tone-signal sources and said output system, gates comprise each: a bypass capacitor coupled between a common-return a. pair of back-to-back diodes coupled in series between path and the junction between said diodes,

one of said tone-signal sources, and said output sysa relatively high resistance and a decay capacitor tem, and coupled between said common return path and said a relatively-high resistance and a decay capacitor coujunction between said diodes, said by-pass capacitors pled between a common return path and the juncbeing scaled so that lower frequency ones of said tion between said back-to-back diodes, said direct tone-signal gates have larger decay capacitors, and voltage being applied via said common switch across a further diode coupled between said common switch said decay capacitors, and and the junction between said relatively-high a further diode coupled between said common switch resistance and said decay capacitor in some at least and the junction between said relatively-high reof said tone-signal gates, said further diodes being sistance and said decay capacitor in at least some so poled as to prevent, discharge of any one said decay capacitors toward asmaller capacitor.

12. The combination according to claim 11, wherein said tone-signals from said sources thereof are complex in harmonic content, and wherein said output system includes:

a low-pass filter,

amplifying means coupled to said low-pass filter, and

electro'acoustic means coupled to said amplifying means.

13. The combination according to claim 12, wherein said tone signals from said sources thereof correspond respectively to C E Git and B 14. The combination according to claim 12, wherein said tone signals from said sources thereof correspond respectively to E Fit and D 15. In an electronic musical instrument, the combination comprising:

a plurality of at least three unharmonic, relativelylow-frequency tone-signal sources having only different fundamental frequencies,

an output system coupled to said tone-signal gates, an equal plurality of direct-current-actuable, gradualwhereby to obtain in said output system a complex decay, tone-signal gates respectively coupled in series low-frequency beat pattern with a gradual decay with said sources, upon opening of said common switch, the decay rates a first source of direct voltage, of said gates being an inverse function of the frea single-pole, single-throw switch in series with said quencies of the tone signals passed by the gates, and wherein said tone-signal sources include frequencies in the ratio selected from the series 1.00, 2.30, 3.60, and wherein said plurality is at least three.

8. The combination according to claim 7, wherein the electroacoustic means coupled to said amplifying means. 9. The combination according to claim 7, includmg:

, first source of direct voltage,

a pulse-forming network coupled between said switch and said tone-signal gates in parallel, said pulse forming network being arranged to produce a pulse of a predetermined constant duration regardless of tone signals from said sources thereof are complex in duration of closure of said switch and arranged to harmonic content, and wherein said output system inprovide a pulse to all said gates which is of the cludes: ;same duration regardless of the duration of closure a low-pass filter, of said switch, amplifying means coupled to said low-pass filter, and an output system, and

a low-pass filter coupled between said tone-signal gates and said output system.

a plurality of diodes respectively in series with at least one less than the number of said tone-signal gates,

16. The combination according to claim 15, wherein said pulse-forming network comprises:

a capacitor coupled between said switch and said tonesaid diodes being poled to pass said gating wave to said gate. =signal gates, 10. The combination according to claim 7, including: a resistively-coupled second source of direct voltage a plurality of diodes respectively in series with all opposite in sign from said first source of direct except the highest frequency one of said tone-signal voltage connected at a point between said switch gates. and one side of said capacitor,

a diode coupled between a common return path and the other side of said capacitor, and

a resistance connected in parallel with said diode.

17. In an electronic musical instrument, the combination comprising:

a plurality of unharmonic, relatively-low-frequency tone signal sources,

an equal plurality of direct-current-actuable, gradualdecay, tone-signal gates respectively coupled in series with said sources,

a first source of direct voltage,

a single-pole, single-throw switch in series with said first source of direct voltage,

a pulse-forming network coupled between said switch and said tone-signal gates in parallel,

an output system, and Y a low-pass filter coupled between said tone-signal gates and said output system,

wherein said pulse-forming network comprises:

a capacitor coupled between said switch and said tonesignal gates,

a resistively-coupled second source of direct voltage op posite in sign from said first source of direct, voltage connected at a point between said switch and one side of said capacitor,

a diode coupled between a common return path and the other side of said capacitor, and

a resistance connected in parallel with said diode, wherein said tone signal gates comprise each:

a pair of back-to-back diodes coupled in series between one of said tone-signal sources and said filter, and -a relatively-high resistance and a decay capacitor coupled in series between a common return path and the junction between said back-to-back diodes, and

a further diode coupled between said pulse'forming network and the junction between said relatively-high resistance and said decay capacitor.

18. In a system for electronically simulating thunder, the combination of at least three sources of signals of unharmonically related frequencies;

an electroacoustic load,

- separate gates for gating each of said signals separately from said sources to said load,

said frequencies of any pair of said frequencies having different frequencies, falling only below forty cycles per second, and

means imparting to said gates each a dilferent sustain time constant, said time constants being an inverse function of the frequencies of said signals and providing audibly sensible differences of decay of said signals down to inaudible level, said frequencies and rates being selected to provide a sound simulating the sound of thunder.

19. The combination according to claim 18 wherein the number of said signals is four.

20. The combination according to claim 18 wherein is further provided means connected intermediate said sources of signals and said electroacoustic load for producing audible heterodyne harmonic and sum and difference heterodyne products of said signals, and

filter means for attenuating at least some of the hormonic products and htesum heterodyne products.

References Cited UNITED STATES PATENTS 3,391,240 7/1968 Uetrecht 841.26 3,223,768 12/1965 Munch 84-1.01 3,333,041 7/1967 Munch 84-l.11 3,037,413 6/1962 Markowitz 84-l.24 3,244,790 4/1966 Sharp 841.13 3,291,886 12/1966 Tinker 841.01 3,196,201 7/1965 McDonald 841.26 2,486,208 10/ 1949 Rienstra 841.26

HERMAN KARL SAALBACH, Primary Examiner C. BARAFF, Assistant Examiner US. Cl. X.R. 84-l.01, 1.11, 1.13 

